1. Field of Invention
This invention relates generally to underwater exhaust systems for marine engines, and in particular to a system installed in a boat whose hull is molded of fiber-reinforced resin, the system including an internal fitting that is integral with the hull and an external fitting telescoped in the internal fitting and extending from the hull to exhaust underwater the cooling water and gases discharged from the operating engine.
2. Status of Prior Art
To propel a boat, the boat machinery for this purpose consists principally of an onboard propulsion engine, a propeller and drive line components. Marine engines are almost exclusively of the familiar internal combustion types, gasoline or diesel. Gasoline engines have traditionally dominated the pleasure and sports boat field, while diesel engines are favored for commercial and military craft.
A typical marine engine includes a water cooling system; hence discharged from the operating engine are cooling water as well as exhaust gases. The boat therefore must be provided with an exhaust system for the discharge. An above water exhaust system for this purpose typically includes exhaust ports exiting through the transom of the boat.
Because of air passing around and behind the transom, exhaust gases are drawn into the cockpit, this being known, as the "station wagon effect." Even at idle, gases still linger at the stern of the boat. Moreover in a following breeze, gases are blown into the cockpit. Not only is the cockpit polluted by noxious exhaust gases, but engine noises are conveyed thereto by the exhaust system, and this makes the cockpit noisy.
A typical underwater exhaust system for a boat has a bronze fitting that is bolted to the hull and extends therefrom into the water. Should the bronze fitting extending From the hull be struck by an object, the fitting itself may not break off, thereby ripping a large hole in the hull with serious consequences.
Motor-driven sports and pleasure boats having hulls molded of fiberglass-reinforced resin are now commonplace. Such hulls must include through-fittings, such as one to accommodate the propeller shaft extending from the engine installed in the boat. And the hull must also include a fitting for an underwater exhaust system for the cooling water and gases discharged from the engine. If this exhaust system is of the conventional type, then it suffers from the above-noted drawbacks.
In our copending Strong et al. application above-identified, there is disclosed a molded fiberglass-reinforced resin boat hull provided with in situ holes to accommodate through-hull fittings, such as a fitting adapted to receive a rudder post.
This boat hull is molded on a female mold having locating holes drilled therein in registration with the holes to be formed in the hull. Anchored by a bolt locked in each locating hole is a plug of non-stick material, such as UHMW polyethylene, which projects above the female mold and has a configuration defining the hole to be formed in situ in the hull. Laid down on the female mold and about the projecting plugs are the reinforcing fiberglass materials which are impregnated with a flowable uncured resin for creating the hull. When the resin is cured, it is not bonded to the plugs whose anchoring bolts are removed to expose the in situ holes. The finished hull is then withdrawn from the female mold. In the case of the in situ hole for receiving a through-hull fitting for a rudder port, the in situ hole for this purpose has an internally-threaded cylindrical extension into which the externally-threaded rudder port is received.
In an underwater exhaust system in accordance with the invention, the system includes an exhaust port formed by an internal fitting which is integral with the molded fiber-reinforced hull. This internal fitting is produced in a manner similar to that in which in situ holes in a molded hull are created in our Strong et al. co-pending application.